The plantation system was significant in American history for at least two main reasons.
First, the plantation system came to define the culture and economy of the South. In that region, the plantations came to dominate the economy. This created an economy that had fewer small businesses and small farms than the North. It also created a society that was aristocratic. The Southern society was not very egalitarian. Instead, it was dominated by plantation owners who thought of themselves as the elite of society.
Second, the plantation system was, of course, based on slavery. The plantation owners needed people to work for them. The conditions in which the people were expected to work were too harsh to attract much in the way of free labor. Instead, the plantation owners used slaves.
These two factors helped very much to lead to the Civil War. The differences in the cultures and economies of the North and South helped to push the two sides apart. The tensions between the two regions eventually caused the Civil War.